Retinal capillary plexus in Parkinson’s disease using optical coherence tomography angiography

AIM:To evaluate the alterations of the retinal microvasculature and foveal avascular zone in patients with Parkinson’s disease(PD)using optical coherence tomography angiography(OCT-A).METHODS:A retrospective study of PD patients examined in the Ophthalmology Department of the General Hospital of Athens,“Georgios Gennimatas”from March 2021 to March 2022 was conducted.Totally 44 patients with PD were included and 18 healthy controls were examined,hence a total of 124 eyes were enrolled in the study.The foveal and parafoveal superficial and deep capillary plexus vascular density(fSCP-VD,fDCP-VD,pSCP-VD,pDCP-CD)and foveal avascular zone(FAZ)were quantified with OCTA.Optical coherence tomography(OCT)was used to measure macular thickness.Our statistical analysis was conducted by using a mixed effect linear regression model.RESULTS:After adjustment for age and gender,the mean parafoveal superficial capillary plexus vascular density(pSCP-VD)and mean parafoveal deep capillary plexus vascular density(pDCP-VD)were significantly decreased in individuals with PD(P<0.001 in both)by-2.35(95%CI-3.3,-1.45)and-7.5(95%CI-10.4,-4.6)respectively.fSCP-VD and fDCP-VD didn’t approach statistical significance.The FAZ area and perimeter were significantly decreased(P<0.001 in both)by-0.1 mm^(2)(95%CI-0.13,-0.07)and-0.49 mm^(2)(95%CI-0.66,-0.32)respectively.Circularity didn’t approach statistical significance.Central retinal thickness(CRT)was significantly decreased in individuals with PD(P<0.001)by-23.1μm(95%CI-30.2,-16)and temporal retinal thickness(TRT)was decreased(P=0.025)by-11μm(95%CI-22,-1.5)while nasal retinal thickness(NRT)only approached statistical significance(P=0.066).CONCLUSION:The mean pSCP-VD,pDCP-VD,CRT and TRT are significantly decreased and FAZ is altered in individuals with PD.These findings can be potentially used as biomarkers for the diagnosis and evaluation of early PD.

Stem cell therapy in retinal diseases

Alteration of the outer retina leads to various diseases such as age-related macular degeneration or retinitis pigmentosa characterized by decreased visual acuity and ultimately blindness.Despite intensive research in the field of retinal disorders,there is currently no curative treatment.Several therapeutic approaches such as cell-based replacement and gene therapies are currently in development.In the context of cell-based therapies,different cell sources such as embryonic stem cells,induced pluripotent stem cells,or multipotent stem cells can be used for transplantation.In the vast majority of human clinical trials,retinal pigment epithelial cells and photoreceptors are the cell types considered for replacement cell therapies.In this review,we summarize the progress made in stem cell therapies ranging from the pre-clinical studies to clinical trials for retinal disease.

Automated Classification of Inherited Retinal Diseases in Optical Coherence Tomography Images Using Few-shot Learning

Objective To develop a few-shot learning(FSL) approach for classifying optical coherence tomography(OCT) images in patients with inherited retinal disorders(IRDs).Methods In this study, an FSL model based on a student–teacher learning framework was designed to classify images. 2,317 images from 189 participants were included. Of these, 1,126 images revealed IRDs, 533 were normal samples, and 658 were control samples.Results The FSL model achieved a total accuracy of 0.974–0.983, total sensitivity of 0.934–0.957, total specificity of 0.984–0.990, and total F1 score of 0.935–0.957, which were superior to the total accuracy of the baseline model of 0.943–0.954, total sensitivity of 0.866–0.886, total specificity of 0.962–0.971,and total F1 score of 0.859–0.885. The performance of most subclassifications also exhibited advantages. Moreover, the FSL model had a higher area under curves(AUC) of the receiver operating characteristic(ROC) curves in most subclassifications.Conclusion This study demonstrates the effective use of the FSL model for the classification of OCT images from patients with IRDs, normal, and control participants with a smaller volume of data. The general principle and similar network architectures can also be applied to other retinal diseases with a low prevalence.

Accuracy improvement for classifying retinal OCT images by diseases using deep learning-based selective denoising approach

In ophthalmology,retinal optical coherence tomography(OCT)images with noticeable structural features help identify human eyes as healthy or diseased.The recently hot arti ficial intelligence(AI)realized this recognition process automatically.However,speckle noise in the original retinal OCT image reduces the accuracy of disease classi fication.This study presents a timesaving approach based on deep learning to improve classi fication accuracy by removing the noise from the original dataset.Firstly,four pre-trained convolutional neural networks(CNNs)from the ImageNet Large Scale Visual Recognition Challenge(ILSVRC)were trained to classify the original images into two categories:The noise reduction required(NRR)and the noise-free(NF)images.Among the CNNs,VGG19 BN performed best with 98%accuracy and 99%recall.Then,we used the block-matching and 3D filtering(BM3D)algorithm to denoise the NRR images.Those noise-removed NRR and the NF images form the processed dataset.The quality of images in the dataset is prominently ameliorated after denoising,which is valid to improve the models'performance.The original and processed datasets were tested on the four pre-trained CNNs to evaluate the effectiveness of our proposed approach.We have compared the CNNs,and the results show the performance of the CNNs trained with the processed dataset is improved by an average of 2.04%,5.19%,and 5.10%under overall accuracy(OA),Macro F1-score,and Micro F1-score,respectively.Especially for DenseNet161,the OA is improved to 98.14%.Our proposed method demonstrates its effectiveness in improving classi fication accuracy and opens a new solution to reduce denoising time-consuming for large datasets.

Convolutional Neural Network-Based Classificationof Multiple Retinal Diseases Using Fundus Images

Use of deep learning algorithms for the investigation and analysis of medical images has emerged as a powerful technique.The increase in retinal dis-eases is alarming as it may lead to permanent blindness if left untreated.Automa-tion of the diagnosis process of retinal diseases not only assists ophthalmologists in correct decision-making but saves time also.Several researchers have worked on automated retinal disease classification but restricted either to hand-crafted fea-ture selection or binary classification.This paper presents a deep learning-based approach for the automated classification of multiple retinal diseases using fundus images.For this research,the data has been collected and combined from three distinct sources.The images are preprocessed for enhancing the details.Six layers of the convolutional neural network(CNN)are used for the automated feature extraction and classification of 20 retinal diseases.It is observed that the results are reliant on the number of classes.For binary classification(healthy vs.unhealthy),up to 100%accuracy has been achieved.When 16 classes are used(treating stages of a disease as a single class),93.3%accuracy,92%sensitivity and 93%specificity have been obtained respectively.For 20 classes(treating stages of the disease as separate classes),the accuracy,sensitivity and specificity have dropped to 92.4%,92%and 92%respectively.

Complications of Ziv-Aflibercept in Choroidal and Retinal Vascular Diseases

Introduction: The modern ophthalmology trends are changing rapidly every day with the introduction of much newer studies and research. Numerous anti-vascular endothelial growth factors (VEGF) are utilized as the mainstay in the treatment of intraocular vascular pathologies. The rationale of this study is to add to the literature regarding the safety and efficacy profile of the ziv-aflibercept as there is insubstantial data in patients with intraocular vascular pathologies being treated with this injection with prime focus on the complications of the injection. Materials and Methods: A prospective observational study was conducted at Opthalmology Department, Lahore General Hospital, Lahore between 14 August 2018 and 23 December 2019. Patients with choroidal and retinal vascular diseases like diabetic macular edema (DME), age-related macular degeneration (AMD) and retinal vein occlusion (RVO) who had no active infection of eye and had no history of myocardial infarction or cerebrovascular accident were added in this study. Results: Best-corrected visual acuity was significantly improved at 4, 8, and 12 weeks as compared to the baseline (p Conclusion: The use of ziv-aflibercept injection via intravitreal route under aseptic conditions for choroidal and retinal vascular diseases is effective as well as safe with mild and treatable ocular side effects.

Pyrroloquinoline quinone:a potential neuroprotective compound for neurodegenerative diseases targeting metabolism

Pyrroloquinoline quinone is a quinone described as a cofactor for many bacterial dehydrogenases and is reported to exert an effect on metabolism in mammalian cells/tissues.Pyrroloquinoline quinone is present in the diet being available in foodstuffs,conferring the potential of this compound to be supplemented by dietary administration.Pyrroloquinoline quinone’s nutritional role in mammalian health is supported by the extensive deficits in reproduction,growth,and immunity resulting from the dietary absence of pyrroloquinoline quinone,and as such,pyrroloquinoline quinone has been considered as a“new vitamin.”Although the classification of pyrroloquinoline quinone as a vitamin needs to be properly established,the wide range of benefits for health provided has been reported in many studies.In this respect,pyrroloquinoline quinone seems to be particularly involved in regulating cell signaling pathways that promote metabolic and mitochondrial processes in many experimental contexts,thus dictating the rationale to consider pyrroloquinoline quinone as a vital compound for mammalian life.Through the regulation of different metabolic mechanisms,pyrroloquinoline quinone may improve clinical deficits where dysfunctional metabolism and mitochondrial activity contribute to induce cell damage and death.Pyrroloquinoline quinone has been demonstrated to have neuroprotective properties in different experimental models of neurodegeneration,although the link between pyrroloquinoline quinone-promoted metabolism and improved neuronal viability in some of such contexts is still to be fully elucidated.Here,we review the general properties of pyrroloquinoline quinone and its capacity to modulate metabolic and mitochondrial mechanisms in physiological contexts.In addition,we analyze the neuroprotective properties of pyrroloquinoline quinone in different neurodegenerative conditions and consider future perspectives for pyrroloquinoline quinone’s potential in health and disease.

Indirubin alleviates retinal neurodegeneration through the regulation of PI3K/AKT signaling

Retinal neurodegenerative disease is a leading cause of blindness among the elderly in developed countries,including glaucoma,diabetic retinopathy,traumatic optic neuropathy and optic neuritis,etc.The current clinical treatment is not very effective.We investigated indirubin,one of the main bioactive components of the traditional Chinese medicine Danggui Longhui Pill,in the present study for its role in retinal neurodegeneration.Indirubin exhibited no detectable tissue toxicity in vivo or cytotoxicity in vitro.Moreover,indirubin improved visual function and ameliorated retinal neurodegeneration in mice after optic nerve crush injury in vivo.Furthermore,indirubin reduced the apoptosis of retinal ganglion cells induced by oxidative stress in vitro.In addition,indirubin significantly suppressed the increased production of intracellular reactive oxygen species and the decreased activity of superoxide dismutase induced by oxidative stress.Mechanically,indirubin played a neuroprotective role by regulating the PI3K/AKT/BAD/BCL-2 signaling.In conclusion,indirubin protected retinal ganglion cells from oxidative damage and alleviated retinal neurodegeneration induced by optic nerve crush injury.The present study provides a potential therapeutic medicine for retinal neurodegenerative diseases.

N-acetylserotonin alleviates retinal ischemia-reperfusion injury via HMGB1/RAGE/NF-κB pathway in rats

AIM:To observe the effects of N-acetylserotonin(NAS)administration on retinal ischemia-reperfusion(RIR)injury in rats and explore the underlying mechanisms involving the high mobility group box 1(HMGB1)/receptor for advanced glycation end-products(RAGE)/nuclear factor-kappa B(NF-κB)signaling pathway.METHODS:A rat model of RIR was developed by increasing the pressure of the anterior chamber of the eye.Eighty male Sprague Dawley were randomly divided into five groups:sham group(n=8),RIR group(n=28),RIR+NAS group(n=28),RIR+FPS-ZM1 group(n=8)and RIR+NAS+FPS-ZM1 group(n=8).The therapeutic effects of NAS were examined by hematoxylin-eosin(H&E)staining,and retinal ganglion cells(RGCs)counting.The expression of interleukin 1 beta(IL-1β),HMGB1,RAGE,and nod-like receptor 3(NLRP3)proteins and the phosphorylation of nuclear factorkappa B(p-NF-κB)were analyzed by immunohistochemistry staining and Western blot analysis.The expression of HMGB1 protein was also detected by enzyme-linked immunosorbent assay(ELISA).RESULTS:H&E staining results showed that NAS significantly reduced retinal edema and increased the number of RGCs in RIR rats.With NAS therapy,the HMGB1 and RAGE expression decreased significantly,and the activation of the NF-κB/NLRP3 pathway was antagonized along with the inhibition of p-NF-κB and NLRP3 protein expression.Additionally,NAS exhibited an anti-inflammatory effect by reducing IL-1βexpression.The inhibitory of RAGE binding to HMGB1 by RAGE inhibitor FPS-ZM1 led to a significant decrease of p-NF-κB and NLRP3 expression,so as to the IL-1βexpression and retinal edema,accompanied by an increase of RGCs in RIR rats.CONCLUSION:NAS may exhibit a neuroprotective effect against RIR via the HMGB1/RAGE/NF-κB signaling pathway,which may be a useful therapeutic target for retinal disease.

Sickle cell retinopathy and systemic disease

Sickle cell disease(SCD)is a widespread hemoglobinopathy that results in significant patient morbidity and mortality.Vascular occlusion can cause acute pain,acute chest syndrome,and avascular necrosis,while hemolysis and endothelial disruption can cause ischemic stroke,leg ulcers,pulmonary hypertension,and priapism.All ocular and orbital structures can be affected by SCD ischemic events,including orbital bone infarction,ischemic optic neuropathy,retinal artery occlusion,hyphema,secondary glaucoma,sickle cell maculopathy,and sickle cell retinopathy.Proliferative sickle cell retinopathy(PSR)is the most common cause of vision loss.Untreated PSR can lead to macular ischemia,vitreous hemorrhage,and tractional retinal detachment.Ophthalmic screening exams and multimodal imaging can lead to earlier detection of sickle cell retinopathy and improved patient outcomes.SCD patients undergoing vitreoretinal surgery may require coordination of care with hematologists to avoid ischemic complications.While hydroxyurea was the only United States Food and Drug Administration approved treatment for several decades,patients with SCD now have several more treatment options.Despite the United States screening all infants for SCD,there can be delays in diagnosis and treatment.This review article aims to provide an overview of sickle disease for the ophthalmologist,and to discuss emerging treatment options and current management of SCD ocular complications.

Game Theory-Based Dynamic Weighted Ensemble for Retinal Disease Classification

An automated retinal disease detection system has long been in exis-tence and it provides a safe,no-contact and cost-effective solution for detecting this disease.This paper presents a game theory-based dynamic weighted ensem-ble of a feature extraction-based machine learning model and a deep transfer learning model for automatic retinal disease detection.The feature extraction-based machine learning model uses Gaussian kernel-based fuzzy rough sets for reduction of features,and XGBoost classifier for the classification.The transfer learning model uses VGG16 or ResNet50 or Inception-ResNet-v2.A novel ensemble classifier based on the game theory approach is proposed for the fusion of the outputs of the transfer learning model and the XGBoost classifier model.The ensemble approach significantly improves the accuracy of retinal disease pre-diction and results in an excellent performance when compared to the individual deep learning and feature-based models.

Retinal thickness and vascular parameters using optical coherence tomography in Alzheimer's disease:a meta-analysis

Examining the retinal tissue has the potential to provide a unique method and technique to quantify Alzheimer’s disease-related changes in participants at various stages of the disease.In this metaanalysis,we aimed to investigate the association of various optical coherence tomography parameters with Alzheimer’s disease and whether retinal measurements can be used to diffe rentiate between Alzheimer’s disease and control subjects.Scientific databases including Google Schola r,Web of Science,and PubMed were systematically searched for published articles that evaluated retinal nerve fiber layer thickness and retinal microvascular network in Alzheimer’s disease and control subjects.Seventy-three studies(5850 participants,including 2249 Alzheimer’s disease patients and 3601controls) were included in this meta-analysis.Relative to controls,Alzheimer’s disease patients had a significantly lower global retinal nerve fiber layer thickness(standardized mean difference [SMD]=-0.79,95% confidence intervals [CI]:-1.03 to-0.54,P <0.00001) as well as each quadrant being thinner in Alzheimer’s disease versus controls.Regarding macular paramete rs,values measured by optical coherence tomography were significantly lower in Alzheimer’s disease than controls for macular thickness(pooled SMD:-0.44,95% CI:-0.67 to-0.20,P=0.0003),foveal thickness(pooled SMD=-0.39,95% CI:-0.58 to-0.19,P <0.0001),ganglion cell inner plexiform layer(SMD=-1.26,95% CI:-2.24 to-0.27,P=0.01) and macular volume(pooled SMD=-0.41,95% CI-0.76 to-0.07,P=0.02).Analysis using optical coherence tomography angiography parameters revealed mixed results between Alzheimer’s disease and controls.Superficial vessel density(pooled SMD=-0.42,95% CI:-0.68 to-0.17,P=0.0001) and deep vessel density(pooled SMD=-0.46,95% CI:-0.75 to-0.18,P=0.001) were found to be thinner in Alzheimer’s disease patients whereas the foveal avascular zone(SMD=0.84,95% CI:0.17-1.51,P=0.01) was larger in controls.Vascular density and thickness of various retinal laye rs were decreased in Alzheimer’s disease patients compared to controls.Our results provide evidence for optical coherence tomography technology having the potential to detect retinal and microvascular changes in patients diagnosed with Alzheimer’s disease and aid in monito ring and early diagnosis methods.

Fundus photography,fluorescein angiography,optical coherence tomography and electroretinography of preclinical animal models of ocular diseases

The eye is an immune-privileged and sensory organ in humans and animals.Anatomical,physiological,and pathobiological features share significant similarities across divergent species(1).Each compartment of the eye has a unique structure and function.The anterior and posterior compartments of the eye contain endothelium(cornea),epithelium(cornea,ciliary body,iris),muscle(ciliary body),vitreous and neuronal(retina)tissues,which make the eye suitable to evaluate efficacy and safety of tissue specific drugs(2).

Mesenchymal stem cell therapy in retinal and optic nerve diseases: An update of clinical trials

Retinal and optic nerve diseases are degenerative ocular pathologies which lead to irreversible visual loss. Since the advanced therapies availability, cell-based therapies offer a new all-encompassing approach. Advances in the knowledge of neuroprotection, immunomodulation and regenerative properties of mesenchymal stem cells(MSCs) have been obtained by several preclinical studies of various neurodegenerative diseases. It has provided the opportunity to perform the translation of this knowledge to prospective treatment approaches for clinical practice. Since 2008, several first steps projecting new treatment approaches, have been taken regarding the use of cell therapy in patients with neurodegenerative pathologies of optic nerve and retina. Most of the clinical trials using MSCs are in Ⅰ/Ⅱ phase, recruiting patients or ongoing, and they have as main objective the safety assessment of MSCs using various routes of administration. However, it is important to recognize that, there is still a long way to go to reach clinical trials phase Ⅲ-Ⅳ. Hence, it is necessary to continue preclinical and clinical studies to improve this new therapeutic tool. This paper reviews the latest progress of MSCs in human clinical trials for retinal and optic nerve diseases.

The role of Toll-like receptors in retinal ischemic diseases

Toll-like receptors（TLRs） are commonly referred to a series of evolutionary conserved receptors which recognize and respond to various microbes and endogenous ligands.Growing evidence has demonstrated that the expression of TLRs in the retina is regulated during retinal ischemic diseases,including ischemia-reperfusion injury,glaucoma,diabetic retinopathy（DR） and retinopathy of prematurity（ROP）.TLRs can be expressed in multiple cells in the retina,such as glial cells,retinal pigment epithelium（RPE）,as well as photoreceptor cells and endothelium cells.Activation of TLRs in retina could initiate a complex signal transduction cascade,induce the production of inflammatory cytokines and regulate the level of costimulatory molecules,which play prominent roles in the pathogenesis of retinal ischemic diseases.In this review,we summarized current studies about the relationship between TLRs and ischemic retinopathy.A greater understanding of the effect of TLRs on ischemic injuries may contribute to the development of specific TLR targeted therapeutic strategies in these conditions.

Beneficial effects of saffron(Crocus sativus L.) in ocular pathologies, particularly neurodegenerative retinal diseases

Saffron(Crocus sativus L.)has been traditionally used in food preparation and as a medicinal plant.It currently has numerous therapeutic properties attributed to it,such as protection against ischemia,as well as anticonvulsant,antidepressant,anxiolytic,hypolipidemic,anti-atherogenic,anti-hypertensive,antidiabetic,and anti-cancer properties.In addition,saffron has remarkable beneficial properties,such as anti-apoptotic,anti-inflammatory and antioxidant activities,due to its main metabolites,among which crocin and crocetin stand out.Furthermore,increasing evidence underwrites the possible neuroprotective role of the main bioactive saffron constituents in neurodegenerative diseases,such as Parkinson’s and Alzheimer’s diseases,both in experimental models and in clinical studies in patients.Currently,saffron supplementation is being tested for ocular neurodegenerative pathologies,such as diabetic retinopathy,retinitis pigmentosa,age-related macular degeneration and glaucoma,among others,and shows beneficial effects.The present article provides a comprehensive and up to date report of the investigations on the beneficial effects of saffron extracts on the main neurodegenerative ocular pathologies and other ocular diseases.This review showed that saffron extracts could be considered promising therapeutic agents to help in the treatment of ocular neurodegenerative diseases.

Intravitreal stem cell paracrine properties as a potential neuroprotective therapy for retinal photoreceptor neurodegenerative diseases

Retinal degenerations are the leading causes of irreversible visual loss worldwide. Many pathologies included under this umbrella involve progressive degeneration and ultimate loss of the photoreceptor cells, with age-related macular degeneration and inherited and ischemic retinal diseases the most relevant. These diseases greatly impact patients' daily lives, with accompanying marked social and economic consequences. However, the currently available treatments only delay the onset or slow progression of visual impairment, and there are no cures for these photoreceptor diseases. Therefore, new therapeutic strategies are being investigated, such as gene therapy, optogenetics, cell replacement, or cell-based neuroprotection. Specifically, stem cells can secrete neurotrophic, immunomodulatory, and anti-angiogenic factors that potentially protect and preserve retinal cells from neurodegeneration. Further, neuroprotection can be used in different types of retinal degenerative diseases and at different disease stages, unlike other potential therapies. This review summarizes stem cell-based paracrine neuroprotective strategies for photoreceptor degeneration, which are under study in clinical trials, and the latest preclinical studies. Effective retinal neuroprotection could be the next frontier in photoreceptor diseases, and the development of novel neuroprotective strategies will address the unmet therapeutic needs.

Retinal imaging in inherited retinal diseases

Inherited retinal diseases(IRD)are a leading cause of blindness in the working age population.The advances in ocular genetics,retinal imaging and molecular biology,have conspired to create the ideal environment for establishing treatments for IRD,with the first approved gene therapy and the commencement of multiple therapy trials.The scope of this review is to familiarize clinicians and scientists with the current landscape of retinal imaging in IRD.Herein we present in a comprehensive and concise manner the imaging findings of:(I)macular dystrophies(MD)[Stargardt disease(ABCA4),X-linked retinoschisis(RS1),Best disease(BEST1),pattern dystrophy(PRPH2),Sorsby fundus dystrophy(TIMP3),and autosomal dominant drusen(EFEMP1)],(II)cone and cone-rod dystrophies(GUCA1A,PRPH2,ABCA4 and RPGR),(III)cone dysfunction syndromes[achromatopsia(CNGA3,CNGB3,PDE6C,PDE6H,GNAT2,ATF6],blue-cone monochromatism(OPN1LW/OPN1MW array),oligocone trichromacy,bradyopsia(RGS9/R9AP)and Bornholm eye disease(OPN1LW/OPN1MW),(IV)Leber congenital amaurosis(GUCY2D,CEP290,CRB1,RDH12,RPE65,TULP1,AIPL1 and NMNAT1),(V)rod-cone dystrophies[retinitis pigmentosa,enhanced S-Cone syndrome(NR2E3),Bietti crystalline corneoretinal dystrophy(CYP4V2)],(VI)rod dysfunction syndromes(congenital stationary night blindness,fundus albipunctatus(RDH5),Oguchi disease(SAG,GRK1),and(VII)chorioretinal dystrophies[choroideremia(CHM),gyrate atrophy(OAT)].

Ex vivo models of retinal neurovascular diseases

Background:The ex vivo model represented by mouse retinal explants in culture is a useful experimental model to investigate the molecular mechanism involved in neurovascular diseases such as diabetic retinopathy(DR).It ensures an experimental overview with more complete respect to isolate cells and reduce problems in terms of accessibility and management with respect to in vivo model.In particular,it allows the evaluation of the relationship between retinal cells in response to the typical stressors involved in DR pathogenesis.Methods:Ex vivo retinal fragments derived from 3-to 5-week-old C57BL/6J mice.In particular,after dissection,the retina is cut into 4 separate fragments and transferred onto inserts placed with ganglion cells up.Once in culture,the explants could be treated in stress conditions typical of DR.In particular,this study protocol describes the procedure for the preparation and the culture of retinal explants with specific metabolic stressors such as high glucose(HG),advanced glycation end product(AGE),and oxidative stress(OS).In the end,this paper provides the protocols to perform molecular analyses in order to evaluate the response of retinal explants to stress and/or neuroprotective treatments.Discussion:The cultured retinal explants represent an ex vivo experimental model to investigate the molecular mechanisms involved in neurovascular diseases such as DR.Moreover,they could be useful to test the effect of neuroprotective compounds in response to metabolic stressors in a fewer time respect to an in vivo model.In conclusion,retinal explants in culture represent a valuable experimental model to conduct further studies to better understand the pathophysiology of DR.

Stem cell therapy for retinal diseases

In this review, we discuss about current knowledge about stem cell(SC) therapy in the treatment of retinal degeneration. Both human embryonic stem cell and induced pluripotent stem cell has been growth in culture for a long time, and started to be explored in the treatment of blinding conditions. The Food and Drug Administration, recently, has granted clinical trials using SC retinal therapy to treat complex disorders, as Stargardt's dystrophy, and patients with geographic atrophy, providing good outcomes. This study 's intent is to overview the critical regeneration of the subretinal anatomy through retinal pigment epithelium transplantation, with the goal of reestablish important pathways from the retina to the occipital cortex of the brain, as well as the differentiation from pluripotent quiescent SC to adult retina, and its relationship with a primary retinal injury, different techniques of transplantation, management of immune rejection and tumorigenicity, its potential application in improving patients' vision, and, finally, approaching future directions and challenges for the treatment of several conditions.